Please note that this is the Narutopedia's article on the ninjutsu used by Yahiko. If you are looking for the article on the ninjutsu used by Kurotsuchi then you should head to Water Release: Water Trumpet.
Water gushes out from the mouth like a waterfall and washes away the enemy. One can freely control the power of this technique with the amount chakra one releases. Having many variations, this is a basic Water Release technique.